720Calvin

@Thomas Perkins Thanks for the heads up on the yoke, I'm really suspecting it has something to do with the driveshaft, maybe a bad yoke, or maybe a weight was knocked loose when they took out the driveshaft to change the U joints. @datzenmike I'll try swapping out the cupped tire with the spare, hopefully that's the issue. I'm just really hoping it doesn't have anything to do with how they installed the new clutch and flywheel. I took a chance on this guy, and probably fixing a poorly balanced flywheel would be just as expensive as the original price to change out the clutch. I do want to put it run it on jack stands to see if I can find where its vibrating from.

The thing I'm not understanding about it though, is why is the vibration so much more pronounced now after the clutch and U joints were changed? The amount of vibration its getting since the service was done is pretty dramatic from how it was before the service. The tires are the same exact ones from before the service was done, so if it did have something to do with the tires, then I would think the vibration after the service was done should be the same as before the service was done.

I don't believe it has a carrier bearing. Yes, just the rear shaft.

The tires are fairly old, but still in ok condition, the previous owner barely drove it. They do have some cupping, but if that is the reason for the vibrations, why is there so much more vibrating now after changing the clutch and U joints? They're still the same tires from before...

Hi Guys, long time lurker first time poster. I have a 1986 Nissan 720 4x4 King Cab 5 speed manual that I purchased about 6 months ago with 115k miles. After buying it, I noticed there was a weird vibration when the car with in 4th or 5th speed and only at 3,000rpm for some reason. The clutch started slipping last week, so I took it to a local mechanic I'd never been to, but had good reviews. I mentioned to him the vibration issue, and he recommended replacing the U joints, which was something I had been planning on doing anyway, so he swapped 4 of the 6 U joints on the drive shaft. I received the car back yesterday and when driving on the freeway, the vibration is now way more pronounced from 2,000 rpm and up in 3rd, 4th, and 5th gears. At 1st and 2nd gears, it doesn't vibrate at any rpm. Any ideas on what could be wrong?